1. Field of the Invention
The present invention relates to a thermal printer apparatus and a printing method for printing in accordance with a thermal conductivity characteristic of thermal paper.
2. Description of the Related Art
It is known that when a thermal printer apparatus performs printing continuously, heat applied to a thermal head on printing is accumulated in the same so that temperature of the thermal head increases. When measuring such a temperature increase by using a temperature sensor, a temperature increase that changes in accordance with the number of printed dots cannot be detected because responsiveness of a temperature sensor for a general use is low. Therefore, there is proposed a technique of predicting a temperature increase of a thermal head by modeling temperature increase characteristics of the thermal head so as to detect the temperature increase in a pseudo manner (see, for example, Patent Document. JP 03-266659 A). Even if fast printing is performed, it is possible to control a quantity of heat to be applied by using the technique considering a temperature increase in the thermal head.
However, according to the technique described in Patent Document JP 03-266659A, as to the temperature increase in the thermal head upon printing, a temperature change is predicted by regarding the number of dots to be printed as a variable and by using a model in which the temperature increase changes in accordance with the number of dots. In addition, heat radiation of the thermal head when not working for printing is predicted by using a model of primary response characteristics due to a time constant determined by a heat radiation constant that is determined in advance. According to the predictions using the models, there is a problem in that if a type or a thickness of the thermal paper changes, a discrepancy occurs in a relationship between the temperature increase characteristics predicted by using a model and an actual temperature increase in the thermal head, which causes deterioration in print quality.